When I cast FURY on an NPC he runs straight to me and starts attacking. This destroys the whole premise of the spell. The spell seems useless without having an insanely high sneak skill, or a low sneak skill and insanely high sneak modifiers. How do people use this spell without sneak?

It has a super long range and if there are 2 npc's standing next to each other they should start fighting.

Is the spell successfully taking hold? If so, maybe try casting it on an enemy who'll have to run past another enemy before reaching you.

What I've found is when you cast it on an enemy, they come to whee the spell was cast, then start to ''frenzy.'' So I usually cast it (out of sneak) and right after, turn invisible.

Like others have said, cast from far out. That should help.

BTW: once you get the hang of this, you'll see why illusion is the best

I have found that when you cast it the person you cast it on often will run to attack you, but other people nearby will attack him (which usually gets his attention away from you and onto them).

That does happen sometimes Andymac, but the unsheathing animation for NPCs takes forever and they sprint like they have the Whirlwind Sprint Thu'um so they usually end up on top of me before any of that happens.